Comparison of percussion laser drilling quality with and without water based ultrasonic assistance

A millisecond-pulsed percussion laser drilling technique using water-based ultrasonic assistance is reported for drilling nickel super-alloy GH4037 sheets with 12-mm-thickness. Influence of ultrasonic vibration on drilling quality including hole taper angle, hole sidewall quality, recast layer microstructure, and hardness distribution of hole heat affected zone (HAZ) is analyzed through comparing holes drilled without ultrasonic assistance. Recast layer reduction, grain refinement, and HAZ hardness increase induced by ultrasonic assistance are also analyzed. It is shown that ultrasonic vibration improves percussion laser drilling quality by reducing hole taper angle, cleaning hole sidewall, decreasing hole defects, reducing recast layer thickness, refining grains, decreasing hole sidewall surface roughness, and increasing micro hardness.